>I bet they are the same 2 devices that had the tzsync.exe problem?
You have just lost your bet. Failing devices are those which has short list of Dev updates and tzsync was working.
I run this command on all four devices:
Get-AppxPackage –AllUsers -Name *MicrosoftWindows.Client.C* | Select Name, PackageFullName
And it give this same result on all devices: Note filter - Name *PARTIAL NAME* in PS command line
ADD:
Applying your fix:
Get-AppxPackage MicrosoftWindows.Client.Core -AllUsers | Reset-AppxPackage
Get-AppxPackage MicrosoftWindows.Client.CBS -AllUsers | Reset-AppxPackage
Remove old versions and now Snip tool is working on all devices.